From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 3 Aug 2018 08:35:08 +0800 From: Ming Lei To: Bart Van Assche Cc: "linux-kernel@vger.kernel.org" , "linux-block@vger.kernel.org" , "jianchao.w.wang@oracle.com" , "axboe@kernel.dk" Subject: Re: [RFC] blk-mq: clean up the hctx restart Message-ID: <20180803003507.GE16047@ming.t460p> References: <20180731045805.GE15701@ming.t460p> <8a3383e6-2926-6858-d8f2-671f3cb9e460@oracle.com> <20180731061616.GF15701@ming.t460p> <42371198-2a4b-1062-3564-411645ffba98@oracle.com> <20180801085841.GA27962@ming.t460p> <9feaa41702ef6fcc00ce1b8aa19bbe179edf4e3f.camel@wdc.com> <20180802165831.GB8928@ming.t460p> <7c933e7e60831f985297d8cc5a540171fc921f44.camel@wdc.com> <20180802171723.GD8928@ming.t460p> <4868e0b82ac6e87aede7fc52da67d3a7913d680b.camel@wdc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <4868e0b82ac6e87aede7fc52da67d3a7913d680b.camel@wdc.com> List-ID: On Thu, Aug 02, 2018 at 05:24:15PM +0000, Bart Van Assche wrote: > On Fri, 2018-08-03 at 01:17 +0800, Ming Lei wrote: > > Not mentioning big CPU utilization is consumed unnecessarily for iterating > > over all queues even though there is only one active queue, is this fair from > > system view? > > I hope that someone will come up some day with a better solution than the > list_for_each_entry_rcu_rr() loop. But as long as such a solution has not yet > been found that loop should stay in order to preserve fair handling of large > numbers of LUNs. Again list_for_each_entry_rcu_rr() isn't fair for small number of active queue in this case, because this way decreases IOPS a lot and consumes CPU much just for checking all thousands of queues unnecessarily, even though 99% of them are idle. Thanks, Ming